This feature aims to improve allow huge pages to be used with libvirt managed guests.

Benefit to Fedora

Enables Fedora KVM hosts to achieve better performance.

Scope

Huge pages support in KVM already exists, so the remaining work is confined to libvirt.

How To Test

mount -t hugetlbfs hugetlbfs /dev/hugepages

Reserve some memory for huge pages - sysctl vm.nr_hugepages=516

Run an existing KVM guest with libvirt with the following added to the guest config:

<memoryBacking>

<hugepages/>

</memoryBacking>

Confirm the guest has booted correctly

Confirm the guest is using hugepages by checking HugePages_Free in </code>/proc/meminfo</code>

User Experience

Users of KVM guests using huge page backed memory should experience improved performance with some savings in host memory consumption. The performance benefit is workload dependent. But we have measured benefits on the order of 20% performance improvement (esp. useful when the guest's workload includes an application which itself is using hugepages).